Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy.
Beat in the egg and vanilla extract until smooth and well combined.
In a separate bowl, whisk together the all-purpose flour, whole wheat flour, baking soda, cinnamon, nutmeg (if using), and salt. Gradually mix the dry ingredients into the wet mixture until fully incorporated.
Fold in the oats and chocolate chips or raisins, ensuring they're evenly distributed.
Chill the dough in the refrigerator for 20-30 minutes. This step helps the cookies maintain their shape and enhances their chewy texture.
Scoop tablespoon-sized balls of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Optional: Sprinkle each cookie with a small pinch of flaky sea salt before baking.
Bake for 10-12 minutes, or until the edges are golden brown and the centers look slightly underbaked. The cookies will set as they cool.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Notes
Chilling the dough enhances the flavor and texture. If you're short on time, chilling for even 10 minutes will help.
You can swap in raisins, dried cranberries, or even chopped nuts for a different twist. Try a mix for the best of both worlds!
Use old-fashioned oats for the chewiest results.
Sprinkle flaky salt before baking for a sweet-savory balance.
Slightly underbake for softer cookies—don’t wait for them to look fully done.
Store with a slice of bread to keep them fresh longer.